Most people are familiar with cephalopods, even if they don't realize it. Those tasty fried calamari, for example, are squid, as are the octopuses you sometimes see on a restaurant menu. But the cephalopod world is huger and more fascinating than the limited taste of the restaurant world, as Wendy Williams demonstrates in her new book Kraken: The Curious, Exciting, and Slightly Disturbing Science of Squid. Here are 14 fun and random facts I found while reading about squid:
1 ) Octopuses have eight arms, and squid and cuttlefish have eight arms and two feeding tentacles (making them decapods). But the nautilus, another type of cephalopod, outnumbers its brethren in terms of appendages: females have around 50 arms while males manage 90 or so. A single nautilus arm is less powerful than other cephalopods,' but the arms are so numerous they can easily overpower prey.
2 ) No species of cuttlefish lives on the East Coast of the United States, but there are more than 100 species that inhabit shallow waters in other parts of the world.
3 ) Some species of squid can swim at speeds up to 25 miles per hour, as fast as some sharks, but only in short spurts.
4 ) The earliest known ancestor of today's squid is Kimberella, a tiny mollusk that looked like a jellyfish and lived about 555 million years ago.
5 ) Neuroscientists in training learn the basics of neurosurgery by practicing on Loligo pealei squid. Their thick axon, thicker than any human nerves, is easier to start with.
6 ) Vampyroteuthis infernalis has been given the inappropriate nickname of "Vampire Squid from Hell." Not only is it not a squid (it's an octopus), it's more coward than predator. When Vampyroteuthis feels threatened, it bites off the end of one of its eight bioluminescent arms, which then floats away, luring a potential enemy with its glowing blue light.
7 ) Some cephalopod ink contains the chemical dopamine, the neurotransmitter that, in human brains, produces the sensation of euphoria. (Scientists don't yet know what role dopamine plays in the squid world, though.)
8 ) The fossils of ammonites---extinct cephalopods that lived 400 to 65 million years ago---were so common on the southern England coast that the town of Whitby had three of them on its town coat of arms. However, the local people thought they were the remains of coiled snakes and added heads to their depictions of the fossils. (The town's current coat of arms still has ammonite fossils on it, but the snake heads have been removed.)
9 ) The tiny deep-sea squid Heteroteuthis dispar is nicknamed the "fire shooter" because it shoots out a cloud of light---from bioluminescent photophores---to distract predators.
10 ) The Hawaiian bobtail squid (Euprymna scolopes) spends its days buried in the sand and hunts only at night. To camouflage itself in shallow, moonlit waters, it takes up luminescent bacteria that help it to blend into its environment.
11 ) Humboldt squid, the large species now commonly found off the coast of California (and on the plates of California restaurants), can practice cannibalism.
12 ) Male paper nautiluses, a type of octopus, are about a tenth the size of the females of the species. The male fertilizes the female by breaking off a special arm, which then swims to the female and deposits spermatophores into her.
13 ) Giant Pacific octopuses can grow up to 400 pounds, though the ones that inhabit aquarium exhibits usually reach only 30 or 40 pounds in size. This species is smart, and aquarium managers are kept busy creating puzzles to challenge the octopuses' brains.
14 ) The Humboldt squid can turn itself blood-red. Because this wavelength of light doesn't travel far underwater, a dark red squid is effectively invisible.